The All Patient Refined DRG is a hybrid classification system based upon basic DRGs and All Patient DRGs. It is more representative of non-Medicare populations, such as pediatric patients, than basic DRGs and contains severity of illness and risk of mortality subclasses. APR-DRGs are based on the principle that severity of illness and risk of mortality are dependent on a patient’s underlying health condition (base APR DRG) and that high severity of illness and risk of mortality are characterized by multiple serious diseases and the interaction of those diseases.1

Purpose/Use:

APR-DRGs are used to severity and risk adjust data for a variety of applications including, quality measurement, payment determinations, case mix adjustments, etc. It is currently being used by CMS for severity adjusting all of Medicare’s hospital discharges.

Coding Family:

ICD-9 & ICD-10

Grouping Methodology:

Diagnosis codes are first grouped into 25 mutually exclusive major diagnostic categories. Diagnosis are then divided into 316 bases APR DRG categories (two of which are error DRGs) in a manner that develops clinically similar patient groups with similar resource intensity. Base APR DRGs are then subdivided into either 1,256 severity of illness subclasses (1. Minor, 2. Moderate, 3. Major, 4. Extreme) or 1,256 risk of mortality subclasses (1. Minor, 2. Moderate, 3. Major, 4. Extreme).2 This methodology results in three hierarchical levels of coding.

Level of Diagnosis Aggregation:

Diagnoses are grouped into 314 base categories and 1256 subclasses.

Number of Codes Included:

Proprietary – Not Available

Number of Codes Excluded:

Proprietary – Not Available

Methodological Considerations:

Evidence suggests that APR-DRGs are strong predictors of resource use. They have been found to have strong performance in terms of R2 in predicting length of stay for hip fracture and pneumonia patients, in particular. APR-DRGS also provide a method to identify utilization patterns and evaluate resource utilization and outcomes among the VA patient population.3

3 McNutt, R et al. Change in MS-DRG assignment and hospital reimbursement as a result of Centers for Medicare & Medicaid changes in payment for hospital-acquired conditions: Is it coding or quality? Quality Management in Health Care. 2010; (19)1:17–24.

Sponsorship:

3M Health Information Systems

Description:

The Medicare Severity Diagnosis Related Groups (MS-DRGs) are payment groups designed for the Medicare population. Patients who have similar clinical characteristics and similar costs are assigned to an MS-DRG. MS-DRGs are linked to a fixed payment amount based on the average cost of patients in the group. Patients can be assigned to an MS-DRG based on their diagnosis, surgical procedures, age and other administrative information. MS-DRGs also recognize severity of illness and resource use, and are based on patient complexity.

Purpose/Use:

MS-DRGs are used by payers, such as CMS to group inpatient services into a global payment amount for hospital stays, based in part on a patient’s diagnosis at discharge.

Coding Family:

ICD-9, ICD-10

Grouping Methodology:

The MS-DRG system builds on the basic DRG system. The system utilizes CMS-DRGs as the foundation for its grouping logic. The logic collapses any paired DRGs (distinguished by the presence of absence of complications or comorbidities (CCs) and/or age) into base DRGs and then splits the base DRGs into CC-severity levels. The general structure of the MS-DRG logic establishes three severity levels for each base DRG: with MCC, with CC, and without CC. In total, diagnoses are grouped into 745 categories.1 This methodology results in two hierarchical levels of coding.

Level of Diagnosis Aggregation:

Diagnoses are grouped under 745 categories.

Number of Codes Included:

Proprietary - Not Available

Number of Codes Excluded:

Proprietary - Not Available

Methodological Considerations:

MS-DRGs have been shown to improve the explanation of cost variation by 9.1 over basic DRGs1 and were developed and refined over a span of years to address the elderly Medicare population. However, this system is also used for neonatal, pediatric and young adult populations, which are very different than most Medicare patients.2

Related Data Sources:

CMS Claims Data

Used in Disease Complexity Research:

No. DRGs are sometimes used in Disease Complexity Research, MS-DRGs are used for reimbursement purposes and research around changes in reimbursement payments.3

The CRG is a classification system that groups all types of patients into single mutually exclusive risk groups based on historical clinical and demographic data to accurately predict healthcare resource use. The underlying clinical principle of this system is that an individual’s severity of illness is highly dependent on the number and severity of the individual’s underlying chronic diagnoses. This classification systems links the clinical and financial aspects of healthcare.1

Purpose/Use:

The CRG is a claims-based classification system used in risk adjustment and to measure a population’s burden of illness.

1. Diagnosis codes are grouped into 37 major diagnostic categories, while procedure codes are grouped into 639 procedure categories. Major diagnostic categories are based on a single organ system of clinical categories.

2. Chronic illnesses are identified and are specified according to their severity.

3. Each patient is assigned to one of 272 mutually exclusive, clinically defined base 3M CRGs according to the combination of primary chronic diseases that are present. Each base 3M CRG is assigned to one of nine hierarchical health status, ranging from catastrophic to healthy, and is then subdivided into discrete severity subclasses based on the severity of chronic diseases. The combination of base 3M CRGs and severity levels results in a total of 1,080 unique clinical groups.

4. The 3M CRGs can be consolidated into three tiers of aggregated 3M CRGs.2

Level of Diagnosis Aggregation:

Diagnosis codes are grouped into 272 clinically-based categories. After the severity scale is applied, diagnosis codes are grouped into 1,080 discrete groups.

Number of Codes Included:

Proprietary - Not Available

Number of Codes Excluded:

Proprietary - Not Available

Methodological Considerations:

3M CRGs are clinically-based, rather than based on a regression risk-adjustment model, which allows providers to link the clinical and financial aspects of healthcare.1 Depending on the level of granularity desired, CRGs can be aggregated to predefined or user-defined aggregated CRG groups that maintain clinical significance and severity. CRGs are also able to take into account the effect of specific interactions between chronic conditions in addition to the interaction of higher and lower levels of severity among conditions.3

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